Clusters of small depressional wetlands store substantial surface water on the agriculturally developed Dougherty Plain. Ecological communities in these wetlands are likely driven by the long term cumulative hydropattern rather than short term weather variation. However, short pulses of inflows and outflows driven by storm events could cumulatively influence long term patterns in wetland hydrology. Hydrologic characterization of these small depressional features can yield insight to wetland biogeochemistry, ecological communities, and surface water storage. The goal of this study was to characterize the hydropattern of 31 isolated wetlands classified by connectivity type. Specific objectives were compare wetland types based on 1) wetland stage frequency distributions; 2) wetland stage duration; and 3) precipitation response. Wetlands were classified by stormflow recurrence interval and storm runoff source as isolated (flow return period > 2 years), forest connected (forest stormflow return period < 2 years) and agricultural connected (agricultural stormflow return period < 2 years). Histograms and empirical cumulative distribution functions (ECDF) were used to analyze stage frequency distributions. Wetland stage duration was compared with stage duration curves and dry day frequency. Additionally, wetland stage response to storms was compared with precipitation response curves.
Results/Conclusions
Isolated wetlands and connected wetlands differed in stage frequency (Isolated – Agriculture p=0.021 and Isolated – Forest p=0.046). Comparison of histograms also indicated that wetland geomorphology is a driver in hydropattern. Wetland types did not differ in dry day frequency. Preliminary analysis of precipitation response curves indicates that both connectivity type and wetland geomorphology drive wetland stage response to storms. In follow up analyses, wetland vegetation types (cypress-gum swamp, marshes, and cypress savannahs) also exhibited differences in stage frequency and differences in mean dry bed frequency. We interpret this data to mean that wetland vegetation types are likely produced, at least in part, by differing hydropatterns. Cypress-gum swamps and marshes had similar stage and dry bed frequency so we believe that they have similar water storage characteristics but may also be driven by longer-term patterns in vegetation recruitment or fire frequency. Hydropattern is important for understanding wetland ecosystems because it drives patterns in nutrient and carbon cycling which in turn influence the biological composition of these depressional features in the Dougherty Plain. Future research should build on this principle to understand the combined effects of connectivity and vegetation type on depressional wetland biogeochemistry as well as ecological structure and function.